Abstract
Globally distributed grasslands are one of the most prominent ecosystem types. Located on every continent, apart from Antarctica, grassland systems provide a wide host of services and provisions. These services and provisions are dependent upon specific biotic communities, and abiotic conditions. Increasingly grasslands are experiencing a change in the community composition of vegetation, most notably in the increase of woody vegetation. The presence and increase of woody vegetation, particularly as a response of time since fire, has been witnessed globally. The commonly occurring shrub Veronica odora has been found to increase in New Zealand tussock grassland systems. The increase of woody vegetation leads to a change in the microhabitat availability within the system and the distribution of the vegetation can provide discrete areas of habitat. Therefore, the relationship between the spatial distribution and the microhabitat provision of the commonly occurring shrub V. odora in a grassland with a known fire history on Mt Benger, Central Otago, was studied. The site informed previous studies with nine 1 ha plots experimentally burned in different seasons (spring burn in November 2000, summer burn in March 2006, and control), to research the effects of fire in New Zealand tussock grassland.
Through the use of drone imagery, individual V. odora were mapped in three previously established plots to obtain the spatial distribution of the shrub population. To understand the role of the shrubs in habitat provisioning the invertebrate community was sampled and identified to order level, from which a Simpsons diversity index measure was calculated. In conjunction with the invertebrate collections from shrubs, turf samples were taken to understand the invertebrate community of the inter-shrub grassland matrix. Finally, the Simpsons diversity of invertebrates associated with the shrubs was assessed in relation to through the spatial distribution of the shrubs.
The results of this study indicate that the V. odora individuals adhere to clustering within a grassland system with a known fire history, on Mt Benger. Invertebrate diversity at the order level does not differ between plots which have undergone fire treatments 15 to 20 years previously, indicating that fire has left no lasting legacy for the invertebrate diversity at the order level associated with shrubs. There is, however, a difference between the invertebrate diversity found on shrubs and the inter-shrub matrix. With regard to the spatial distribution of the V. odora and the associated invertebrate diversity, there was no statistically significant difference between the variables.